They’re participating in the 15th annual 135 Arrowhead, a grueling three-day race beginning in International Falls and ending in Tower, Minnesota. Participants bike, run, or ski across the remote Arrowhead snowmobile trail with limited assistance for 135 miles.

Named one of the 50 most challenging races in the world, the race is infamous for its low completion rate -- race director Ken Krueger expects a finish rate of less than 50 percent this year. (Track the progress of those still out there by clicking here.)

“Our historic average is a 57 percent finish, and we’ve seen as low as 20,” Krueger adds.

Frigid temperatures across the state have forced schools and businesses to close down, but these extreme conditions are exactly what Arrowhead racers are looking for. Duluth's Leah Gruhn, the first female biker to cross the finish line at 5:45 a.m. Tuesday, said the trail’s grueling conditions is what makes the race attractive to endurance racers.

On the men's side, Jordan Wakely didn't just finish. He shattered the record for fastest finish ever, arriving in Tower 11 hours and 43 minutes after getting on his bike. That's nearly 90 minutes faster than the previous record for best time ever, according to the Duluth News Tribune, which reports Neil Beltchenko of Minneapolis came in second... at 13 hours, 27 minutes, well off Wakely's historic pace. (Beltchenko raced "unsupported," unlike Wakely.)

This year’s start in International Falls saw air temperatures of 10 degrees below zero. Historically, this is only slightly colder than the average temperature racers have faced since Arrowhead 135’s inauguration in 2005. According to race directors, it was 28 degrees below zero at the beginning of the race in 2007.

Participants are well aware of the freezing conditions. Every appendage is covered with multiple insulating layers. Race directors inspect racers at gear check to make sure everyone is well-protected and safe.

The rules even tell participants to bring a whistle to call for help in case of an emergency, because their mouths may “be too numb to yell.”

As of 7 p.m. Tuesday, 34 bikers have finished the course. Out of the 146 bikers, runners, and skiers who began, 90 have already dropped out.

After finishing the race, Gruhn said she had some shallow frostbite in areas of her body. She said she’s not concerned about weather conditions, just as long as she doesn’t experience any permanent damage.

“I want to have the ability to go outside in winter in the future without sensitivity to frostbite, and that’s more important to me than finishing or finishing quickly,” she said.

How do these athletes stay motivated during such a long race through remote parts of northern Minnesota? By keeping their eye on the checkpoints, Kruger said. It’s not about the finish line, but rather what’s coming up next.

Although the race is largely unsupported, one checkpoint serves hot soup and grilled cheese sandwiches, a luxury that Gruhn said was a “highlight.” Otherwise, racers carry their own food and belongings.

The arduous shared journey racers endure creates an unbreakable connection, Gruhn said. The roster is mostly filled with veterans who have at least started the race multiple times, so each year it’s like a family reunion.

“You’re all dealing with the same challenges, and you might not be with them, but you’re on the same trail at the same time,” Gruhn said. “It creates a deep bond and a deep understanding.”

Even just signing up for the race and showing up to the starting line generates an immense amount of pride for participants. Gruhn, a nine-time participant, says Arrowhead 135 has given her the confidence to race in other biking events around the country.

Krueger himself participated in the race multiple times before he became the current race director with his wife, Kim.

“After I finished it the first time I said I would never, ever do it again, and that was probably 13 years ago,” Krueger said.

If you think anyone who attempts this race is absolutely bonkers, you’re not alone. But it’s surging in popularity, causing race directors to limit the rosters in order to maintain solitude on the desolate trail.

“People may think we’re crazy, but there’s a lot of us,” Krueger said. “It’s an adventure. Everyone has their own different idea of adventure.”